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Reply to Comments on “Analysis of Equilibrium Acid Distribution in the System of Citric Acid-Water-(Triisooctylamine + Methyl Isobutyl Ketone) Using a Quasi-Physical Approximation” Wiratni, Boma W. Tyoso, and Wahyudi B. Sediawan* Department of Chemical Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia
Sir: In our paper “Analysis of Equilibrium Acid Distribution in the System of Citric Acid-Water(Triisooctylamine + Methyl Isobutyl Ketone) Using a Quasi-Physical Approximation”,1 we presented experimental data at four temperatures (301, 320, 329, and 338 K), three mathematical models, and the model’s constants obtained from the experimental data. In the evaluation of the constants, we applied a linear regression method. Recently, Dr. P. Salim showed in his paper that the constants of model II give a poor data fit, especially at 329 K (with an average of absolute relative error of 72.30%) and at 338 K (with 116.81% error). He also proposed the use of the nonlinear regression method, which gives a better data fit. Having recalculated the model’s constants using the same method as that applied in our paper (linear regression), we found that there were miscalculations at the two temperatures. The constants of model II at 329 K should be KTi ) 2.2081, φ ) 0.2118, and η ) 0.9615 (for the same value of Kf as in our paper) and those at 338 K KTi ) 4.1336, φ ) 0.2755, and η )1.1404 (for the same value of Kf as in our paper), with the * To whom correspondence should be addressed. Phone: 62-274-902171. Fax: 62-274-902170. E-mail: wbsrsby@ indosat.net.id.
averages of absolute relative error at 329 and 338 K being 13.55% and 12.54%, respectively. We agree that the simultaneous nonlinear regression of all of the constants (Kf, KTi, φ, and η) will, of course, give a better data fit. However, in our paper, to better test of the validity of the models presented, we chose the independent multistep linear regression described in the paper. For example, the value of Kf was obtained independently from the data of the nonreacting system (CTi,tot ) 0), while the others were obtained from the reacting system data. We thank Dr. P. Salim very much for his interest and comments on our paper. He helped us to find the miscalculations. Furthermore, the suggested constants obtained by the nonlinear regression, which give a better data fit, support the usefulness of model II. To the readers, we apologize for the mistakes and the inconvenience that resulted. Literature Cited (1) Wiratni; Tyoso, B. W.; Sediawan, W. B. Analysis of Equilibrium Acid Distribution in the System of Citric Acid-Water(Triisooctylamine + Methyl Isobutyl Ketone) Using a QuasiPhysical Approximation. Ind. Eng. Chem. Res. 2001, 40, 668.
IE010720U
10.1021/ie010720u CCC: $22.00 © 2002 American Chemical Society Published on Web 12/08/2001
